It’s inside a underground warehouse, where several hundred thousand film canisters line the towering shelves at Underground Vaults & Storage.

“As far as the older titles, ‘Gone with the Wind,’ ‘Voyage to the Bottom of the Sea,’ ” says manager Brian Corwin.

Keeping tabs on the collection is part of Corwin’s job. The movie companies won’t let him reveal what’s there to prevent thieves from stealing the assets, but the labels hint at the contents inside each canister: copies of some of the most recognizable movies in cinematic history.

“The films are distributed geographically across the United States so if there’s a disaster in one place, they don’t lose all their assets,” Corwin says.

The refrigerated vault is kept at a chilly 45 degrees. The humidity is regulated at 35 percent. With these conditions, “you can get about 100 years out of the material, if not more than that,” Corwin says.

This 60,000-square-foot warehouse beneath Kansas City is a like a single grain of sand on a beach. It’s part of a vast underground complex known as SubTropolis, which in all amounts to more than 6 million square feet of leased industrial space.

“It would take 42 Arrowhead Stadiums to fill the developed portion of SubTropolis,” says Mike Bell, referring to the venue where the Kansas City Chiefs play football.

Bell is a vice president of Hunt Midwest, the company that owns and leases the space. The company is able to capitalize on it by a fluke of nature. Eons ago, a shelf of limestone formed just below modern-day Kansas City. Miners dug that limestone out of the earth and over the decades left behind an impressive network of caves.

When the ore ran out, a new business was born.

“In the 1960s was when the first tenant occurred,” Bell says. “It was a construction company. They just put their equipment here over the wintertime. They didn’t have to pay to winterize it because of the natural temperature of the underground.”

Ford Motors, Russell Stover and Pillsbury were also early tenants. Today, the U.S. Postal Service keeps rare stamps there. A local food company promotes its “cave-aged” cheese.

But SubTropolis isn’t just about storage. Ground Effects, a company that installs bedliners and custom automotive graphics, benefits from the climate-controlled conditions deep underground.

On the Ground Effects production line, a dozen or so brand-new Ford F-150 pickup trucks wait to enter an automated booth where a robot will spray on a new bedliner.

“If it’s too cold you can’t apply a graphic. If it’s too hot, it might warp something,” says manager April Adams, who has worked underground for a decade — and appreciates not having to scrape snow and ice off her car in the winter.